Flanagan can’t do horror
He’s a writer-director of some talent who is pretty good at character and drama, but he rarely creates tension or scares.
Most of his horror is the tedious someone wakes up, looks over there and suddenly a dark figure is standing there accompanied by the 100th thud sound effect.
Meanwhile directors like David Lynch can truly get under your skin with the uncanny.
Check out this 1 minute amateur horror, Flanagan could learn a lot from watching this: https://youtu.be/gNQIdEv-Emo